Ceria-zirconia mixed oxide was successfully synthesized via the sol-gel process at ambient temperature, followed by calcination at 500, 700 and 900 • C. The synthesis parameters, such as alkoxide concentration, aging time and heating temperature, were studied to obtain the most uniform and remarkably high-surface-area cubic-phase mixed oxides. The thermal stability of both oxides was enhanced by mutual substitution. Surface areas of the Ce x Zr 1−x O 2 powders were improved by increasing ceria content, and their thermal stability was increased by the incorporation of ZrO 2 . The most stable cubic-phase solid solutions were obtained in the Ce range above 50 mol%. The highest surface area was obtained from the mixed catalyst containing a ceria content of 90 mol% (200 m 2 /g). Temperature programmed reduction results show that increasing the amount of Zr in the mixed oxides results in a decrease in the reduction temperature, and that the splitting of the support reduction process into two peaks depends on CeO 2 content. The CO oxidation activity of samples was found to be related to its composition. The activity of catalysts for this reaction decreased with a decrease in Zr amount in cubic phase catalysts. Ce 6 Zr 4 O 2 exhibited the highest activity for CO oxidation.
This work is focused on the ceria zirconia mixed oxide prepared through a surfactant-introduced synthesis method. High surface area nanoparticle mesoporous ceria/zirconia-mixed oxide was successfully synthesized and characterized using various techniques. High surface area mesoporous fluorite-structured CeO 2 -ZrO 2 was obtained from the elimination of surfactants upon calcination. A surface area in excess of 205.6 m 2 /g was obtained after calcination at 500• C, and dropped to 75.96 m 2 /g by heating at 900• C. Temperature-programming reduction (TPR) results showed that the lowest reduction temperature was obtained from the sample containing 40% zirconia content.
The viscoelastic behavior of different ceria gelling systems prepared through sol-gel transition were investigated by the rheological measurement. The gelation time was observed by the frequency independence of tand, and increased with increasing acid:alkoxide molar ratio. At the gel point, both storage and loss moduli (G’µ wn, G” µ wn)exhibited a power law dependence of applied frequency with n’ = n” = n. The viscoelastic exponents and gel strength parameter were dependent on the composition of system. The increase in HCl:alkoxide molar ratio increased the n value while decreased the S parameter.
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